1. Field of the Invention
An object of the present invention of the method for crimping a contact on strands of a cable. It can be used more particularly in the field of electrical connections, especially in aeronautics, where the connection between a cable and a contact needs to be reliable irrespectively of the external conditions to which it is subjected. These electrical connections are generally subjected to very wide-ranging variations of pressure and temperature because they are installed in aircraft that may fly at altitudes of up to 10,000 meters. For example, for an aircraft, the temperature may vary from −50° C. in the air to +40° C. on the ground.
Furthermore, the variations occur rapidly and are undergone in a span of some hours. The cables are used to connect electronic systems to one another or to a power supply. It is therefore vital to ensure the security of these connections. To this end, the invention is aimed at reducing the consequences of differential expansion phenomena induced by these temperature variations. To do this, the invention proposes a method to ensure the satisfactory crimping of the contact on the cable even when the contact and the cable are made of different materials.
The invention also proposes a solution to ensure the crimping of a contact forming a barrel or sleeve within which the cable is placed so that the sleeve covers bared strands of the cable and, at the same time, a non-bared portion of this cable. In general, the core of a cable is made out of unitary strands which may be made of aluminum, especially for avionics applications. These strands may also be made of copper or similar materials. The strands are surrounded by an insulator sheath generally made of a plastic. The constraint that arises when the cable comprises strands is that the strands may roll around one another during a crimping operation. Furthermore it becomes difficult to hold the contact, even when it is crimped, on these divided wires. It is an object of the invention to overcome these drawbacks related to mechanical behavior and electrical continuity by proposing to connect the contact to the core, namely the strands of the cable, and at the same time to the sheath of the cable.
2. Brief Description of the Prior Art
In the prior art, the patent document FR-A-2,710,788 teaches a crimping method to connect a bared end of an electrical cable to a contact in order to ensure the impervious sealing of the connection. To use the method, the contact should have a barrel or sleeve with a tapered outer rim, this sleeve enabling the cable to be received. This contact is made out of a malleable and conductive material. According to a known method, the crimping is done by wire drawing. One end of the contact is held in the crimping tool while the jaw of the crimping tool is shifted along the tapered rim and folds the sides of the rim along the cable and along the bared end.
In general, the contact which is designed to receive a bared end of a cable in the sleeve has a connection termination at a second end. The contact has a flange between this connection termination and the zone presenting the sleeve. In the invention, it is planned to retain the contact inside the crimping tool at the level of this flange. Indeed, the flange is presented inside a means for holding the crimping tool. Then, after the end of the cable to be crimped has been inserted into the sleeve, the jaw is shifted from the flange-holding means toward the aperture of the sleeve in order to crush the sides of this sleeve on the cable. The shifting of the sleeve exerts radial pressure and, at the same time, axial pressure on the strands of the cable to be crimped. With such a method, there is a risk of disengaging the strands from the sleeve, and even breaking them inside the sleeve, thus giving rise to a connection fault.
The solution of the invention ensures the connection of the strands in the sleeve and, at the same time, their integrity and the impervious sealing of the connection thus made. The impervious sealing of the connection is fundamental to preventing corrosion phenomena. In particular, the present connection using the crimping method according to the invention gives connections that withstand temperature variations and also corrosion by salt spray or salt mist.
It is an object of the invention to carry out the crimping of a contact in which a bared end of the cable is inserted into a sleeve of this contact. Crimping is done at a first level, at a first zone of the sleeve surrounding bared strands of the cable, by a radial clamping motion of a jaw. And to crimp the sleeve throughout its length along this cable end, the closed position of the tool that achieves the first crimping is maintained so as to ensure the position of the strands of the cable relative to the sleeve. Thus, when the sleeve is crimped throughout its length by wire drawing, it is ensured that the length of the strands crimped within the sleeve has a length of engagement that truly corresponds to the planned dimensions. Indeed, the strands of the cable are neither pushed back nor broken inside the sleeve during-the wire drawing operation.